How to Check If an IBAN Is Valid (and What Validation Can't Tell You)

An IBAN (International Bank Account Number) identifies a bank account for transfers across Europe and many other countries. One wrong character and the payment bounces — or worse, gets delayed for days. A quick check catches most typos before you send.

Anatomy of an IBAN

Take the example GB82 WEST 1234 5698 7654 32:

• GB — country code.
• 82 — two check digits.
• WEST 1234 5698 7654 32 — the national account number (BBAN), whose format depends on the country.

Each country has a fixed length: 22 characters for Germany and the UK, 27 for France and Italy, 24 for Spain, 25 for Portugal, 29 for Brazil.

How the check digits work

Move the first four characters to the end, convert letters to numbers (A = 10 … Z = 35), and divide the resulting big number by 97. A valid IBAN leaves a remainder of 1. This "mod-97" check catches every single-character mistake and almost every swap of two adjacent characters.

Checking one or a whole list

Paste an IBAN into the IBAN validator, or paste a list with one per line. It checks country, length and mod-97, and for several countries (such as Spain, Belgium and Norway) also the national check digits inside the account number. It formats the result in groups of four. Nothing is sent anywhere — the check runs in your browser.

What validation can't tell you

• Whether the account exists or is open.
• Who owns it. A fraudster's IBAN is perfectly valid. If someone emails "new bank details", confirm by phone using a number you already have.
• Whether the bank supports the payment type you're making.

Invoicing a business in the EU? Check their VAT number format too with the EU VAT number checker.